Characterization of oils of hazelnuts from Asturias,Spain

Nine varieties of virgin hazelnut oil from different autochthonous cultivars from distinct locations in Asturias (Spain) were obtained by extraction under a pressure of 280 kg/cm² at a temperature of 45 °C. The extracted oils were separated and filtered. The overall composition (percentages of husk, oil and moisture) of unhusked seeds was determined as well as moisture, ash, total sulfur and heat power of the husks for their possible use as biomass. Recovery of the oil extraction procedure for its application to the production of extra virgin edible hazelnut oil was studied. Fatty acid, tocopherol and sterol compositions as determined by capillary column gas chromatography and triglyceride compositions as determined by high performance liquid chromatography are reported in this study. All values were compared with a Turkish and a French hazelnut oil, with solvent‐extracted hazelnut oil and with a 75/25 blend. A cluster analysis was performed as a criterion to differentiate the different hazelnut oils as groups.     

Formation of short‐chain glycerol‐bound oxidation products and oxidised monomeric triacylglycerols during deep‐frying and occurrence in used frying fats

Heating fats and oils at high temperature in the presence of air, a common procedure in culinary practices such as frying, results in a complex mixture of oxidation products. These compounds may impair the nutritional value of the food. Among them, there is a growing interest in the group of oxidised triacylglycerol monomers because of their high absorbability. The main structures in this group include triacylglycerols (TG) containing short‐chain acyl groups formed by homolytic β‐scission of the alkoxy radicals coming from allylic hydroperoxides. In addition there are TG containing oxidised fatty acyl groups of molecular weight similar to that of their parent TG, i.e., epoxy, keto and hydroxy fatty acyl groups. In this review, the main routes of formation of oxidised TG monomers are detailed. Also, the most relevant advances in the analysis of intact TG molecules by high‐performance liquid chromatography coupled with mass spectrometry are discussed. Special attention is paid to the present analytical possibilities for accurate quantification of the most important oxidised compounds formed at high temperature. Both the need to convert fats and oils into simpler derivatives, thus concentrating the compounds bearing the oxidised structure, and the methylation procedure selected to avoid artefact formation are justified. Typical concentrations of short‐chain fatty acids, short‐chain aldehydic acids, short‐chain diacids, and monoepoxy fatty acids, ketoacids and hydroxyacids in frying oils from restaurants and fried‐food outlets, with polar lipids levels at the limit of rejection for human consumption, are given.     

Margarine and shortening oils by interesterification of liquid and trisaturated triglycerides

Liquid vegetable oils (VO), including cottonseed, peanut, soybean, corn, and canola, were randomly interesterified with completely hydrogenated soybean or cottonseed hardstocks (vegetable oil trisaturate; VOTS) in ratios of four parts VO and one part VOTS. Analysis of the reaction products by high-performance liquid chromatography showed that at 70°C and vigorous agitation, with 0.5% sodium methoxide catalyst, the reactions were complete after 15 min. Solid-fat index (SFI) measurements made at 50, 70, 80, 92, and 104°F, along with drop melting points, indicated that the interesterified fats possess plasticity curves in the range of commercial soft tub margarine oils prepared by blending hydrogenated stocks. Shortening basestocks were prepared by randomly interesterifying palm or soybean oil with VOTS in ratios of 1:1 or 3:1 or 4:1, respectively. Blending of the interesterified basestocks with additional liquid VO yielded products having SFI curves very similar to commercial all purpose-type shortening oils made by blending hydrogenated stocks. Other studies show that fluid-type shortening oils can be prepared through blending of interesterified basestocks with liquid VO. X-ray diffraction studies showed that the desirable β′ crystal structure is achieved through interesterification and blending. Presented at AOCS Annual Meeting & Expo, Atlanta, Georgia, May 8–12, 1994.     

Effects of Simvastatin on Lipid Metabolism in Wild-Type Mice and Mice with Muscle PGC-1α Overexpression

Previous studies suggest that statins may disturb skeletal muscle lipid metabolism potentially causing lipotoxicity with insulin resistance. We investigated this possibility in wild-type mice (WT) and mice with skeletal muscle PGC-1α overexpression (PGC-1α OE mice). In WT mice, simvastatin had only minor effects on skeletal muscle lipid metabolism but reduced glucose uptake, indicating impaired insulin sensitivity. Muscle PGC-1α overexpression caused lipid droplet accumulation in skeletal muscle with increased expression of the fatty acid transporter CD36, fatty acid binding protein 4, perilipin 5 and CPT1b but without significant impairment of muscle glucose uptake. Simvastatin further increased the lipid droplet accumulation in PGC-1α OE mice and stimulated muscle glucose uptake. In conclusion, the impaired muscle glucose uptake in WT mice treated with simvastatin cannot be explained by lipotoxicity. PGC-1α OE mice are protected from lipotoxicity of fatty acids and triglycerides by increased the expression of FABP4, formation of lipid droplets and increased expression of CPT1b.     

Determination of milk fat in chocolates by gas-liquid chromatography of triglycerides and fatty acids

The combination of two routine methods is proposed to determine the content of milk fat (MF) in chocolates, which is applicable even in the presence of lauric fats or others. The content of MF is obtained from the sum of C₄₀, C₄₂, and C₄₄ medium-chain triglycerides, determined by capillary gas-liquid chromatography (GLC). A new method, based on methyl esters of lauric acid and on minor acids situated between myristic and palmitic, is proposed. It enables detection and estimation of potential lauric fats, as well as the determination of the actual content of MF. The influence of other vegetable and animal fats is discussed. We analyzed 45 MF samples extracted from industrial milk powders and from pure or fractionated MF for chocolate manufacturing or pastry by GLC of triglycerides. We also analyzed by capillary GLC the methyl esters from 22 of those fats. Mixtures of these 22 MF samples with a cocoa butter also were used for chromatographic analyses of methyl esters and triglyceride. Results from the various analytical methods have been presented.     

Chemical and physical properties of the solid fats in commercial soft margarines

The fats of ten Canadian soft margarines were crystallized from acetone at 15°C to obtain the high-melting glycerides (HMG). The solid fats in the margarines were extracted with isboutanol at 5°C. X-ray diffraction showed that the canola margarines were in the β crystal form, the soybean and sunflower-palm-palm kernel margarines in the β′ form, while those of canola-palm and another sunflower-palm-palm kernel margarines contained a mixture of β′ and β forms. X-ray diffraction of the isolated solids showed additional short spacings compared with those of the original margarines. Differential scanning calorimetry heating curves of the solids were compared with those of the HMG. The melting temperatures of the HMG were 10°C higher than the solids. It is suggested that the polymorphic behavior of soft margarines is related to the chemical composition of the HMG and the solids. Solids in margarines can also be provided by interesterification of palm oil products. Presented at the Annual Meeting, Canadian section of AOCS, October 18–19, 1990, Toronto, Canada.     

Thermoxidation of substrate models and their behavior during hydrolysis by porcine pancreatic lipase

The behavior of thermoxidized triacylglycerols during hydrolysis catalyzed by porcine pancreatic lipase was evaluated using nonpolar triacylglycerols isolated from palm olein (NPTPO), triolein, and sn-1,3 diolein substrates. Substrates were thermoxidized at 180°C for 1 to 4 h. Owing to formation of polymers and dimers of triacylglycerols, the molecular weight of the thermoxidized substrates increased. After 1 h heating, the concentration of polymers and dimers was similar for the sn-1-3 diolein and triolein samples but higher in NPTPO samples. Conjugated double bonds were formed in all samples, and α,β-unsaturated carbonyl compounds developed through allylic oxidations. These caused increased ultraviolet absorbance at 232 nm. The hydrolysis of heated and unheated samples by the lipase can be described by a Michaelian equation. The enzyme showed a higher apparent V _max and K _M with heated sn-1,3 diolein and triolein than with their unheated counterparts. This was due to the generation of polar compounds which acted as emulsifiers and which favored the formation of an oil/water microemulsion. This behavior was not observed in NPTPO, where heating decreased the apparent V _max and K _M over the first 2 h. Later, a tendency to increase these values was observed. The results could be explained by a balance between concentration of surfactants and of natural emulsifiers in the thermoxidized samples.     

Water-in-triglyceride oil emulsions. Effect of fat crystals on stability

The influence of low concentrations (0.1-5%) of fat crystals on the stability of water-in-soybean oil emulsions was examined by light scattering and sedimentation experiments. Both the initial flocculation/coalescence rate and long-term stability against water separation were determined. The initial flocculation/coalescence rate increased upon addition of small amounts of fat crystals. When the crystal concentration was increased above a critical concentration (specific to a system), a decrease in the flocculation/coalescence rate occurred. The increased flocculation/coalescence rate is likely the effect of bridging of water droplets by fat crystals. Fat crystal wetting by water is an important criterion for this phenomenon to occur. Emulsion stabilization for crystal concentrations above critical is caused by a mechanical screening of water droplets. The presence of considerable amounts of crystals in oil also lowered the density difference between droplet and medium, and enhanced viscosity. The degree of increase in viscosity depended upon the emulsifier. Both a decrease in density difference and an increase in viscosity play a role in hindering flocculation/coalescence of droplets. In long-term studies of water separation, all concentrations of fat crystals stabilized the water-in-oil emulsions. The droplet size of these emulsions increased until the critical droplet size was approached where the screening effect of crystals on the droplets no longer stabilized the emulsions. The stabilizing effect for emulsions with monoolein was continuously improved by increasing the amount of crystals up to 5%. For lecithin-stabilized emulsions, an optimal effect was achieved for fact crystal concentrations of 1–2%.     

线性回归在糖尿病诊断中的应用

将数据挖掘技术应用到糖尿病的诊断之中,运用线性回归算法,对糖尿病患者体检的历史记录进行数据处理,分析糖化血红蛋白和甘油三酯与糖尿病之间的关系,以发现其中的医学诊断规则和模式,辅助医生进行疾病的诊断.根据数据挖掘的结果分析糖尿病患者的数据,得出结论：糖化血红蛋白和甘油三酯在人体内的含量越高,患糖尿病的概率就越大.     

Modulated temperature differential scanning calorimetry for examination of tristearin polymorphism: I. Effect of operational parameters

The transformations of tristearin were examined by modulated temperature differential scanning calorimetry (MTDSC) in order to study the effect of operational parameters on the nature of information obtained from this technique. Tristearin has been used as a model polymorphic system showing metastable phases and complicated transformation routes occurring at relatively slow rates. The parameters examined were underlying heating/cooling rates and the amplitude of modulation. The first conclusion is that MTDSC enables overlapping α-melting and β-crystallization events to be separated, thus increasing the information obtained compared to normal thermal analysis. Other general conclusions are that observation of reversible processes is strongly influenced by the underlying heating rate; low to moderate heating rates are recommended. Amplitude of modulation has a complicated effect on the phenomenon being studied; when studying systems that exhibit metastable or polymorphic transitions, it is recommended that a range of amplitudes be tested to enable confirmation of whether an observed ‘recrystallization’ effect is a new phase or the same phase as the one melting. Cooling with modulation disturbs the crystallization process, possibly leading to smaller or imperfect crystals; however, the phases obtained are not different compared to normal DSC. The usefulness of MTDSC in analyzing these types of complicated systems is primarily qualitative at the moment. Some recommendations have been made as to the combinations of parameters for studying such systems.